Methods and apparatus for EMI shielding in multi-chip modules

ABSTRACT

Methods and structures provide a shielded multi-layer package for use with multi-chip modules and the like. A substrate ( 102 ) (e.g., chip carrier) has an adhesive layer ( 104 ), where electronic components ( 106, 108 ) are attached. An insulating layer ( 110 ) is formed over the plurality of electronic components, and a conductive encapsulant structure ( 115 ) is formed over the insulating layer. The adhesive layer is detached from the electronic components, and multi-layer circuitry ( 140 ) is formed over, and in electrical communication with, the plurality of electronic components. A shielding via ( 150 ) is formed through the multilayer circuitry such that it contacts the conductive encapsulant.

FIELD OF THE INVENTION

The present invention generally relates to semiconductor assemblies and,more particularly, to methods of providing electromagnetic shielding formulti-chip modules and related packages.

BACKGROUND OF THE INVENTION

Semiconductor devices continue to decrease in size and increase inpower-density, resulting in a number of challenges for system designers.One of the primary challenges relates to electromagnetic interference(EMI)—i.e., how to shield the internal components from each other aswell as from external sources. Such shielding is particularly importantin the context of multi-chip and multi-module RF integration.

Chip-to-chip and module-to-module shielding is often provided using anembedded shield structure, a metal can cover, conformal shieldingstructures, or the like. However, such solutions tend to increase thesize of the component, and generally require additional processing stepsand cost.

Accordingly, there is a need for high-performance, low-cost shieldingtechniques for use with multi-chip and multi-module assemblies.Furthermore, other desirable features and characteristics of the presentinvention will become apparent from the subsequent detailed descriptionand the appended claims, taken in conjunction with the accompanyingdrawings and the foregoing technical field and background.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and

FIGS. 1-6 depict an example process for manufacturing a multi-chipmodule in accordance with one embodiment;

FIG. 7 is an isometric overview of a multi-chip module in accordancewith one embodiment and at one point in the process depicted in FIGS.1-6;

FIGS. 8-13 depict an example process for manufacturing a middle panellayer in accordance with one embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, or the following detailed description. For the sake ofbrevity, conventional techniques related to semiconductor processing,electronic packaging, and device assembly are not described herein.

For simplicity and clarity of illustration, the drawing figures depictthe general structure and/or manner of construction of the variousembodiments. Descriptions and details of well-known features andtechniques may be omitted to avoid unnecessarily obscuring otherfeatures. Elements in the drawings figures are not necessarily drawn toscale: the dimensions of some features may be exaggerated relative toother elements to assist improve understanding of the exampleembodiments.

Terms of enumeration such as “first,” “second,” “third,” and the likemay be used for distinguishing between similar elements and notnecessarily for describing a particular spatial or chronological order.These terms, so used, are interchangeable under appropriatecircumstances. The embodiments of the invention described herein are,for example, capable of use in sequences other than those illustrated orotherwise described herein. Unless expressly stated otherwise,“connected” means that one element/node/feature is directly joined to(or directly communicates with) another element/node/feature, and notnecessarily mechanically. Likewise, unless expressly stated otherwise,“coupled” means that one element/node/feature is directly or indirectlyjoined to (or directly or indirectly communicates with) anotherelement/node/feature, and not necessarily mechanically.

The terms “comprise,” “include,” “have” and any variations thereof areused synonymously to denote non-exclusive inclusion. The terms “left,”right,” “in,” “out,” “front,” “back,” “up,” “down,” and other suchdirectional terms are used to describe relative positions, notnecessarily absolute positions in space. The term “exemplary” is used inthe sense of “example,” rather than “ideal.”

In general, the present invention relates to methods and structures forshielding semiconductor packages using conductive molding compound suchthat both local and global shielding can be achieved. Referring to thesimplified cross-sectional illustrations shown in FIGS. 1-6, anexemplary EMI shielding method will now be described.

As shown in FIG. 1, a carrier structure or “substrate” 102 having anadhesive layer (e.g., an adhesive tape) 104 is provided. Next, as shownin FIG. 2, one or more electronic components (106, 108, etc.) areattached to surface 105 of adhesive layer 104. These electroniccomponents may be RF components, microprocessors, capacitors, resistors,or any other type of active or passive component, depending upon theparticular application. In the illustrated embodiment, a “glob top”surface acoustic wave (SAW) structure 108 and semiconductor component106 are shown. However, the embodiments are not limited as to type ornumber of components. It will also be appreciated that while anindividual multi-layer structure is shown in the figures, it is possibleto create multiple structures simultaneously, then singulate individualstructures for testing.

As illustrated in FIG. 3, an insulating layer 110 is formed overelectronic components 106 and 108 as well as, optionally, any exposedareas of adhesive layer 104. Next, as illustrated in FIG. 4, aconductive molding compound or “encapsulant” 115 is formed overinsulating layer 110. Conductive molding compound 115 may comprise anymaterial that provides structural support for the embedded componentsand at the same time exhibits an electrical conductivity suitable forproviding the desired EMI shielding, for example, conductive plasticcompounds that contain both plastic and metallic components, which havethe electromagnetic properties of metal but can be processed like aplastic.

As shown in FIG. 5, the substrate 102 and adhesive layer 104 have beenremoved, and for clarity the resulting structure is shown inverted.Thus, what was originally the underside of components 108 and 106 is nowexposed, along with portions of insulating layer 110, forming a surface120.

Next, multilayer circuitry 140 is formed, as shown in FIG. 6, such thatit is in electrical communication with the various electricalcomponents. Multilayer circuitry 140 includes various interconnects,dielectrics, multi-layer metallization, and other components that allowelectrical communication between layers. In the illustrated embodiment,for example, signal vias 152 are shown contacting components 106 and108. The processing of such layers is well known in the art. The size,shape, and thicknesses of the various layers that make up multi-layerstructure 140 may be selected to meet any particular design objectives.In one embodiment, for example, layers 140 have a combined thickness ofapproximately 20 to 200 microns.

Next, as shown in FIG. 6, one or more shielding vias 150 are formed suchthat they extend through multilayer circuitry 140 and contact conductiveencapsulant 115. Shielding vias 150 might consist of conventional platedvias traditionally used in connection with printed circuit board (PCB)technology, or might be metal-filled (e.g., copper-filled) viastructures. Furthermore, multiple thermal via layers may be formed bysuccessive plating and etching to form vertical stacks of such vias. Theshape, thickness, spacing, density, and size of the vias may vary. Forexample, they may be spaced in a regular array, a staggered array, arandom pattern, or any other suitable configuration.

In this way, the components 106 and 108 are shielded from each other viaconductive compound 115 and substrate shielding via 150, which may be inthe form of an internal or peripheral via ring.

It will be appreciated that the FIGS. 1-6 are simplified for the purposeof clarity, and that a typical finished structure might also include anynumber of passive and active components. For example, various basebandICs, transceivers, power management modules, and the like may be used inan exemplary application. Additional information regarding such embeddedchip structures may be found, for example, in U.S. Pat. No. 6,838,776and U.S. Pat. No. 6,921,975, owned by the present assignee.

In accordance with another embodiment, a local shielding layer may beformed before applying conductive molding compound. Such structures areshown in the isometric view FIG. 7, wherein components 106, 108 areattached to conductive non-contiguous shielding regions 170. Suchshielding layer may comprise epoxy, ceramic, or the like. In a furtherembodiment, a top shielding layer may be formed on the conductiveencapsulant 115 if, for example, the components are exposed after athinning process.

While the present invention may be used in conjunction with a number ofdifferent packages and processes, one such process is redistributed chippackage (RCP) process. Referring to the simplified process illustratedin the isometric diagrams of FIGS. 8-13, a substrate 802 is coated withan adhesive 804 (FIG. 8). Next, a mold frame 806 is secured to thesurface of the adhesive 804 (FIG. 9), and a number of die 808 (or otherelectronic components) of the same or varying types are placed, activeside down, along with one or more other components, in a predeterminedpattern on tape 804 (FIG.10). An insulating layer, as previouslydescribed, may be formed over components 808 at this point.

An epoxy or other encapsulant material 810 (e.g., a conductive epoxy) isdeposited onto the assembly such that it covers die 808 andsubstantially fills up the space there between (FIG. 11). Next, moldframe 806 is removed (FIG. 12). The surface of encapsulant 810 can beground down to the desired thickness, where layer 115 still covers thetop of the components. Then, layers 804 and 802 are released, the panelis cleaned, and the backside (device I/O) surface of the individual dieor other components 808 are exposed (FIG. 13). The resulting panel layerstructure is then suitably processed (for example, as discussed hereinwith respect to the embodiment of FIG. 6) to form build-up layers orother multi-layer structures, including vias and the like, usingconventional methods. It will be appreciated that various additionalsteps involving cleaning, curing, and/or baking might also be performedat various times in the process.

In accordance with one embodiment, a method of manufacturing amulti-layer package structure includes: providing a substrate having anadhesive layer thereon; attaching a plurality of electronic componentsto the adhesive layer; forming an insulating layer over the plurality ofelectronic components; forming a conductive encapsulant structure overthe insulating layer; detaching the adhesive layer from the electroniccomponents; forming multi-layer circuitry over, and in electricalcommunication with, the plurality of electronic components; and forminga shielding via through the multilayer circuitry such that it contactsthe conductive encapsulant. The method may further include forming alocal insulating layer on the adhesive layer prior to forming theconductive encapsulant. Another embodiment further includes reducing thethickness of the conductive encapsulant layer. In another, the methodfurther includes the step of forming a top shielding layer on theconductive encapsulant structure. In one embodiment, the conductiveencapsulant comprises conductive plastic mold compound. In another,forming the insulating layer includes depositing a polymer layer.Forming the multilayer circuitry may include forming at least one signalvia for transmitting signals between the plurality of components.

A shielded multi-layer package structure in accordance with oneembodiment comprises: a conductive encapsulant structure; a plurality ofelectronic components embedded within the conductive encapsulantstructure, wherein an insulating layer is provided between theconductive encapsulant structure and the electronic components;multi-layer circuitry provided on and in electrical communication withthe plurality of electronic components; and at least one shielding viaextending through the multilayer circuitry such that it contacts theconductive encapsulant. The package may further include a localinsulating cover layer between at least one of the plurality ofelectronic components and the conductive encapsulant. Another embodimentfurther includes a top shielding layer provided on the conductiveencapsulant structure. In a further embodiment, the conductiveencapsulant comprises a conductive plastic mold compound. In oneembodiment, forming the insulating layer includes depositing a polymerlayer.

A method of shielding a plurality of electronic components fromelectromagnetic interference (EMI) includes: embedding the plurality ofelectronic components within a conductive encapsulant structure suchthat insulating layer is provided between the conductive encapsulantstructure and the electronic components; and forming at least oneshielding via in electrical contact with the conductive encapsulant. Amethod further includes forming multi-layer circuitry in electricalcommunication with the plurality of electronic components. In anotherembodiment, the method further includes forming a local insulating layerbetween at least one of the plurality of electronic components and theconductive encapsulant. In another embodiment, forming the localshielding layer includes forming a layer of epoxy or ceramic. A topshielding layer may be provided on the conductive encapsulant structure.In various embodiments, the conductive encapsulant may comprise amaterial selected from the group consisting of aluminum, copper, nickeliron, tin, and zinc. In one embodiment, the insulating layer is providedby depositing a polymer layer. In another, depositing the polymer layerincludes depositing a polyimide layer.

The exemplary embodiment or exemplary embodiments presented above areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing the exemplary embodiment orexemplary embodiments. It should be understood that various changes canbe made in the function and arrangement of elements without departingfrom the scope of the invention as set forth in the appended claims andthe legal equivalents thereof.

1. A method of manufacturing a multi-layer package structure,comprising: providing a substrate having an adhesive layer thereon;attaching first surfaces of a plurality of electronic components to theadhesive layer, wherein the plurality of electronic components have thefirst surfaces and second surfaces that are opposite the first surfaces;forming an insulating layer with first portions disposed in contact withthe second surfaces of the plurality of electronic components and withsecond portions disposed in contact with the adhesive layer; forming anelectrically conductive encapsulant structure over the insulating layer,resulting in a structure in which the first portions of the insulatinglayer are positioned between the conductive encapsulant structure andthe second surfaces of the plurality of electronic components, and inwhich the second portions of the insulating layer are positioned betweenthe adhesive layer and the conductive encapsulant structure; detachingthe adhesive layer from the first surfaces of the plurality ofelectronic components and the second portions of the insulating layer;forming multi-layer circuitry over, and in electrical communicationwith, the first surfaces of the plurality of electronic components; andforming a shielding via through the multilayer circuitry and the secondportions of the insulating layer such that the shielding via directlycontacts the conductive encapsulant structure.
 2. The method of claim 1,further including forming a local insulating layer on the adhesive layerprior to forming the conductive encapsulant.
 3. The method of claim 1,further including reducing the thickness of the conductive encapsulantlayer.
 4. The method of claim 1, wherein the conductive encapsulantcomprises conductive plastic mold compound.
 5. The method of claim 1,wherein forming the insulating layer includes depositing a polymerlayer.
 6. The method of claim 1, wherein forming the multilayercircuitry includes forming at least one signal via for transmittingsignals between the plurality of components.
 7. A method of shielding aplurality of electronic components from electromagnetic interference(EMI), wherein the plurality of electronic components have firstsurfaces and second surfaces that are opposite the first surfaces,comprising: embedding the plurality of electronic components within anelectrically conductive encapsulant structure such that first portionsof an insulating layer are provided between the electrically conductiveencapsulant structure and the second surfaces of the electroniccomponents, and such that second portions of the insulating layer areprovided between the plurality of electronic components and coplanarwith the first surfaces; forming at least one shielding via through thesecond portions of the insulating layer and in electrical contact withthe electrically conductive encapsulant structure; and formingmulti-layer circuitry over, and in electrical communication with, thefirst surfaces of the plurality of electronic components, wherein the atleast one shielding via directly contacts the electrically conductiveencapsulant structure through the multi-layer circuitry and the secondportions of the insulating layer.
 8. The method of claim 7, furtherincluding forming a local insulating layer between at least one of theplurality of electronic components and the conductive encapsulant. 9.The method of claim 7, wherein forming the local shielding layerincludes forming a layer of epoxy or ceramic.
 10. The method of claim 7,wherein the conductive encapsulant comprises a material selected fromthe group consisting of aluminum, copper, nickel iron, tin, and zinc.11. The method of claim 7, wherein the insulating layer is provided bydepositing a polymer layer.
 12. The method of claim 10, whereindepositing the polymer layer includes depositing a polyimide layer.